1. FIELD OF THE INVENTION
This invention relates to a flying type magnetic head to be used for a magnetic recorder and a method of manufacturing the same.
2. DESCRIPTION OF THE PRIOR ART
In a magnetic recorder used as the external memory of a computer, a gap spacing between a magnetic recording medium (hereinafter referred to as a "magnetic disk") and a magnetic recording/reproducing head (hereinafter referred to as a "magnetic head") has a large influence on a recording density. The smaller the spacing is, the higher a recording density becomes. To hold the gap spacing between the magnetic disk and the magnetic head in a magnetic disk apparatus, a flying type magnetic head is used in which a slider for holding the magnetic head is approached onto the rotating magnetic disk to fly the slider slightly above the magnetic disk surface by means of an air flow upon rotation of the magnetic disk.
At present to access a recorded track on a magnetic disk, a swing arm type actuator is employed. In this actuator, a slider is held at the end of a suspension supported at one point, and the slider is so moved as to shake its head from the inner periphery to the outer periphery of the magnetic disk or vice versa at its fulcrum as a center and positioned at a predetermined track.
In such a flying type magnetic head, there arises a variation in a flying height due to the speed difference between the magnetic disk and the magnetic head at the inner and outer peripheries of the magnetic disk, and a variation in the flying height due to an air inflow angle (hereinafter referred to as a "skew") of the magnetic disk with respect to the slider at the inner and outer peripheries of the magnetic disk. Thus, the flying height varies according to the position of the track.
The flying height of the magnetic head largely has an influence on recording and reproducing characteristics of the magnetic head. Thus, the variation in the flying height described above is a large problem in the magnetic disk apparatus. Accordingly, a constant flying height slider for holding a constant flying height of the magnetic disk at any position of the magnetic disk is desired.
On the other hand, when the magnetic disk is stopped steadily, the magnetic head is in contact with the magnetic disk. When the magnetic disk starts to rotate, the air starts to flow into between the magnetic disk and the magnetic head, and fence the magnetic head starts to fly. Accordingly, at the time of starting, the magnetic disk and the magnetic head are in a sliding state for a certain period. Thereafter, the magnetic head flies from the magnetic disk. To enhance the reliability, the sliding state of the magnetic head is preferably as short as possible. In addition when the magnetic head is temporarily deviated from the stable state due to external disturbance, it is desirable to be able to restore quickly the stable state without contact with the magnetic disk.
As described above, it is desired in the magnetic disk apparatus using the present flying type magnetic head that the flying height of the magnetic head of the magnetic disk apparatus is always constant on the inner and outer peripheries of the magnetic disk, the time required for flying the magnetic head at the time of starting (hereinafter called a "take-off time") is as short as possible and a restoring force against external disturbance is large.
The above-described characteristics of the magnetic disk apparatus largely depend upon the shape of the surface of the slider opposed to the magnetic disk (hereinafter called a "fluid lubricating surface"). Thus, the sliders which have various fluid lubricating surfaces have been developed at present. The shapes of the sliders have been growing complicated year after year. Therefore, the processing of the slider becomes impossible only by the conventional mere grinding technique, and hence precise processing techniques such as an ion milling or an optical etching using optical exposure technique starts to be introduced.
However, these techniques lead to an increase in processing steps, resulting in a decrease in the yield of products. Simultaneously, its manufacturing cost increases.
To solve such inconveniences, a tripad slider was recently disclosed from Read Write Co. FIG. 10 is a perspective view showing this tripad slider. This slider is considered as one of the excellent sliders which has a short take-off time and low flying height characteristics.
In FIG. 10, rails 3 and 4 extend in the longitudinal direction of a slider 2 for forming a magnetic head and are formed at the right and left sides of the fluid inflowing side of the upper surface of the slider 2, i.e., the fluid lubricating surface. A protrusion 5 isolated at the fluid discharge side is provided at the rear end face 6 of the slider 2 in the same height as the rails 3 and 4. Recording and reproducing heads 7 are mounted at the center of the rear end face 6 of the slider 2.
As shown in FIG. 11, the rails 3, 4 and the protrusion 5, i.e., the fluid lubricating surfaces are, opposed to the magnetic disk 8. A flow occurs in the fluid by the rotation of the magnetic disk 8, and hence the magnetic recording and reproducing heads 7 are slightly flying above the magnetic disk 8 by the fluid bearing action.
The features of this flying type magnetic head 1 are:
1) the possibility of processing the fluid lubricating surface by the conventional grinding, PA1 2) stable floating in a low flying height, and PA1 3) short take-off time.
The rails 3 and 4 of the slider each have an oblong shape, and are terminated at the vicinity of the central part of the slider. The protrusion 5 having the same height as those of the rails 3 and 4 is provided at a central groove between the rails 3 and 4 at the rear part of the slider. This structure causes the machining of the slider surface to be very difficult. More specifically, since the grinding of the slider surface must retain the protrusion 5 at the central part, the grooving must be stopped on the midway. Further, several stripes of perpendicular ground grooves must be combined under control. The smaller the size of the slider becomes, the more difficult the processing becomes.
The flying characteristics of this slider are shown in FIGS. 12(a) and 12(b). FIGS. 12(a) and 12(b) show the results of the simulations of the flying height (a distance between the end of the magnetic head and the surface of the magnetic disk) and the pitching (the difference of the flying height between the fluid inflow end and discharge end of the slider) of the slider along the radial direction of the magnetic disk by altering the area of the fluid lubricating surface (corresponding to curves A, B and C in the drawings).
When the curve B in FIG. 12(a) is observed as one example of the flying characteristics, the flying height is 25 nm on the inner periphery of the magnetic disk and 43 nm on the outer periphery of the magnetic disk. In the case of this slider, the variation in the flying height of the magnetic head on the inner and outer peripheries of the magnetic disk is +72%. Similarly, the pitching of the slider increases as the radius of the slider increases. That is, when the curve B in FIG. 12(b) is observed, the variation in the pitching of the slider increases by 50% on the outer periphery of the magnetic disk.
The protrusion 5 of this slider has a surface substantially perpendicular to the fluid inflow direction. The perpendicular surface of the slider feasibly causes a problem of a head crush due to the adhesion and retention of dust in the air. In this case, to form the shape for reducing the retention of the dusts, it is impossible to grind the shape and must employ complicated processing steps such as ion etching to form the shape used in the process.
FIG. 13 shows the variation in the flying height of the slider in terms of the depth of the ground groove for reference. When the depth of the groove becomes 1 .mu.m or more, the variation in the flying height is eliminated. That is, with the groove of 1 .mu.m or less, the characteristics of the slider largely alter according to the depth of the groove, but if the groove of 1 .mu.m or more is formed, constant flying characteristics can be obtained. Therefore, this slider can incorporate sufficiently stable flying characteristics with high mechanical grinding accuracy.